The invention relates to the manufacture of a tubular part that includes an insert made of a metal matrix composite.
In the field of aeronautics in particular, a constant objective is to optimize the strength of parts for a minimal mass and minimal size. Thus, certain parts may hereafter include an insert made of a metal matrix composite. Such a composite comprises a metal alloy matrix, for example a titanium (Ti) alloy matrix, in which fibers extend, for example silicon carbide (SiC) ceramic fibers. Such fibers have a tensile strength well above that of titanium (typically, 4000 MPa as opposed to 1000 MPa). It is therefore the fibers that take up the loads, the metal alloy matrix providing the function of binding with the rest of the part and also the function of protecting and insulating the fibers, which must not come into contact with one another. Furthermore, ceramic fibers are resistant to erosion but must necessarily be reinforced by metal.
These composites may be used in the manufacture of disks, shafts, cylinder actuator bodies, casings, spacers, such as reinforcements for monolithic parts such as blades, etc. The dimensions, especially the thickness, and the mass of these parts may thus be considerably reduced. To give an example, a blade-supporting disk may be reduced to a simple ring.
To obtain such an insert made of a composite, filaments called “coated filaments”, each comprising a ceramic fiber coated with metal, are formed beforehand. The metal gives the filament the elasticity and flexibility necessary for being handled. Preferably, a very thin carbon or tungsten filament lies at the center of the fiber, along its axis. This carbon filament is coated with silicon carbide, while a thin layer of carbon is interposed between the fiber and the metal so as to provide a diffusion barrier/buffer function during the differential thermal relaxation that occurs upon cooling the liquid metal deposited on the fiber.